813 warm up time
My Collins KWM-2 uses a home brew power supply. Step start on filaments -
at correct voltage and no high voltage for 60 seconds. Same tubes in it for
30 years. I think the only two power amplifier tubes that failed were
dropped on the floor. Some amplifiers adjusted the filament voltage to be
correct and some were never measured.
I ran a 3 x 813 amp for years and never changed the tubes or even measured
the filament voltage. Just used a transformer with the rated voltage and
called it good. Unless the filament transformer has a current rating much
higher than the demands of the amplifier tubes, the surge will probably be
ok.
Incidently, the home brew equipment looks practical. I built a vfo using
the Collins 70H3. The problem with it is that it covers 1.5 to 3 MHz with
10 turns. That is 150 kHz per turn. Bad for a linear dial. I used a 8:1
reduction gear and a crystal controlled mixer to cover 5 to 6.5 MHz, then
limited use to 5 - 5.5 MHz. That was coupled in as the second vfo for my
Drake TR-5, so when I switch it in, the Drake digital dial displays the
frequency. Extremely stable. Oh, I converted it to solid state, also,
which is easy to do. There is one minor problem in that there are no stops
on the dial. Not a problem for me, but if some kid came in and started
twisting, he could break something. Oh well, you need to take some risks in
life.
73, Colin K7FM
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